Temperature Effects on Purification of Eutrophic Water by Floating Eco-island System.

Temperature effects on pollutant removal from hypereutrophic water by a floating eco-island system (FEIS) planted with N. officinale and O. javanica were evaluated. The concentration of NH₄-N was dramatically decreased by both planted FEIS (P-FEIS) and non-planted FEIS (NP-FEIS), while NO₂-N concentration decreased by more than 20 times in the P-FEIS only, at low (10°C), medium (22°C), and high (35°C) temperatures. The P-FEIS could decrease NO₃-N concentration over 1-3 times depending on temperature, with greater extent at 35°C. The total P (TP) removal reached 78% by  the P-FEIS at all temperatures, over 3 times greater than those by the NP-FEIS. The removal rates of Chla, COD_Mn, and BOD₅ by the P-FEIS were 70-83% at 22 °C and 35 °C, and much higher than those by the NP-FEIS. The N. officinale had higher efficiency in removing NH₄-N and TN at 10°C, and BOD₅ at 22°C and 35 °C, whereas O. javanica more effectively decreased Chla at 22 °C and 35 °C and COD_Mn at 10°C than N. officinale. The O. javanica appears to be superior in lowering DO and pH than N. officinale. These results indicate that O. javanica and N. officinale planted FEIS had great potential for purifying hypereutrophic water, especially at low temperature season.